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Federal Register / Vol. 86, No. 108 / Tuesday, June 8, 2021 / Proposed Rules
AS355N, and AS355NP helicopters; and certain Model AS350B3 helicopters. AD
20210415 requires repetitive visual inspections of the right-hand side of the vertical fin spar for cracking, and corrective action if necessary. The FAA
issued AD 20210415 to address cracking in the spar of the upper part of the vertical fin and fractures in the front attachment screws. This condition could lead to in-flight separation of the upper part of the vertical fin, resulting in loss of control of the helicopter.

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Actions Since AD 20210415 Was Issued The preamble to AD 20210415
explains that the FAA was considering further rulemaking to address the actions specified in paragraph 2 of EASA AD 20200186, dated August 20, 2020. The FAA has now determined that further rulemaking is indeed necessary, and this proposed AD
follows from that determination. This proposed AD would require additional actions and would expand the applicability to include additional Airbus Helicopters Model AS350B3
helicopters i.e., Model AS350B3
helicopters modified through Eurocopter AS350 Service Bulletin 55.00.14 in service. Eurocopter AS350
Service Bulletin 55.00.14 was optional terminating action in EASA AD 2020
0186. However, helicopters modified by Eurocopter AS350 Service Bulletin 55.00.14 are affected by fatigue cracking and must be inspected. A terminating action is not included in this proposed AD.
The EASA, which is the Technical Agent for the Member States of the European Union, has issued EASA AD
20210099, dated April 9, 2021 EASA
AD 20210099 also referred to as the Mandatory Continuing Airworthiness Information, or the MCAI, to correct an unsafe condition for all Airbus Helicopters Model AS355E, AS355F, AS355F1, AS355F2, AS355N, and AS355NP helicopters; and all Model AS350B3 helicopters except those that have that embodied Airbus Helicopters Modification 073148 in production.
EASA stated that recent analysis identified that AS350B3 helicopters modified through Eurocopter AS350
Service Bulletin 55.00.14 any revision in service might also be affected by the identified unsafe condition.
This proposed AD was prompted by a determination that additional actions are required to address the unsafe
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condition and additional helicopters are affected by the identified unsafe condition. This proposed AD was also prompted by a report that, during an unscheduled post-flight inspection of the tail cone area of an Airbus Helicopters Model AS355NP helicopter, a crack was found in the spar of the upper part of the vertical fin and fractures were found in the two front attachment screws. Airbus Helicopters Model AS350B3 helicopters have a similar vertical fin configuration and are subject to comparable load levels as the affected Model AS355NP helicopter, therefore, this model may be subject to the same unsafe condition revealed on the Model AS355NP helicopter. The FAA is proposing this AD to address cracking in the spar of the upper part of the vertical fin and fractures in the front attachment screws. This condition could lead to in-flight separation of the upper part of the vertical fin, resulting in loss of control of the helicopter. See the MCAI for additional background information.
Related Service Information Under 1
CFR Part 51
EASA AD 20210099 specifies procedures for repetitive visual inspections of the right-hand side of the vertical fin spar for cracking; repetitive cleaning and repetitive detailed inspections for cracking of the vertical fin spar and vertical fin upper attachments; and corrective action. The corrective action includes repair.
This material is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in the ADDRESSES section.
FAAs Determination and Requirements of This Proposed AD
These products have been approved by the aviation authority of another country, and are approved for operation in the United States. Pursuant to the bilateral agreement with the State of Design Authority, the FAA has been notified of the unsafe condition described in the MCAI referenced above. The FAA is proposing this AD
after evaluating all the relevant information and determining the unsafe condition described previously is likely to exist or develop in other products of these same type designs.
Explanation of Retained Requirements Although this proposed AD does not explicitly restate the requirements of AD

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20210415, this proposed AD would retain all of the requirements of AD
20210415. Those requirements are referenced in EASA AD 20210099, which, in turn, is referenced in paragraph g of this proposed AD.
Proposed AD Requirements This proposed AD would require accomplishing the actions specified in EASA AD 20210099 described previously, as incorporated by reference, except for any differences identified as exceptions in the regulatory text of this AD.
Explanation of Required Compliance Information In the FAAs ongoing efforts to improve the efficiency of the AD
process, the FAA initially worked with Airbus and EASA to develop a process to use certain EASA ADs as the primary source of information for compliance with requirements for corresponding FAA ADs. The FAA has since coordinated with other manufacturers and civil aviation authorities CAAs to use this process. As a result, EASA AD
20210099 will be incorporated by reference in the FAA final rule. This proposed AD would, therefore, require compliance with EASA AD 20210099
in its entirety, through that incorporation, except for any differences identified as exceptions in the regulatory text of this proposed AD.
Using common terms that are the same as the heading of a particular section in the EASA AD does not mean that operators need comply only with that section. For example, where the AD
requirement refers to all required actions and compliance times, compliance with this AD requirement is not limited to the section titled Required Actions and Compliance Times in the EASA AD. Service information specified in EASA AD
20210099 that is required for compliance with EASA AD 20210099
will be available on the internet at https www.regulations.gov by searching for and locating Docket No.
FAA20210453 after the FAA final rule is published.
Costs of Compliance The FAA estimates that this proposed AD affects 650 helicopters of U.S.
registry. The FAA estimates the following costs to comply with this proposed AD:

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